Microporous films, which are generally employed as interlayer insulating films for semiconductor devices having multi-layer interconnect structures, exhibit easier absorbability of moisture contained in the air or the like, and thus modifications such as hydrophobic treatment and the like are conducted. The compatibility between the characteristic of allowing a modifier rapidly uniformly penetrating into a microporous film and the characteristic of allowing the surplus amount of a modifier remained after the treatment being immediately exhausted, is required for modifying the surface of the microporous film with the modifier. A diameter of a pore in a microporous film, which is employed in an interlayer insulating film of a semiconductor integrated circuit device, is sufficiently smaller than the pattern size, and more specifically equal to or smaller than 5 nm. Therefore, a modifying gas or a modifying chemical solution cannot be easily reached to the pore surface in the inside of the microporous film.
As a technology for hydrophobizing a microporous film formed on a substrate, for example, Patent Document 1 describes a hydrophobic treatment for a microporous film formed on a substrate, in which a gaseous organosilane compound having hydrophobic group is introduced in a hydrophobic processor and then the hydrophobic treatment is conducted at a temperature ranging from 0 degree C. to 450 degrees C.
Patent Document 2 describes that a hydrophobization of a medium-porous oxide film is achieved by diffusing a silylation agent in a silylation process for the medium-porous oxide film on a substrate at a temperature ranging from about 25 degrees C. to about 200 degrees C.
Patent Document 3 describes that a substrate is cooled to a temperature ranging from about 100 Kelvin to about 300 Kelvin to easily cause a condensation of a hydrophobizing agent on a wafer, and then the wafer is heated to a temperature ranging from about 300 degrees C. to about 450 degrees C. in order to activate the hydrophobizing agent.
Patent Document 4 describes that a surface of a nano-porous silica is coated with a reinforcement agent (silylation agent) in a form of a vapor or a liquid, and then the coated surface is dried, and then is baked at a maximum temperature up to 425 degrees C. In addition, the disclosure also deliberately includes an aspect, in which a mixture of 50% of hexamethyldisilazane of (HMDZ) and 50% of 3-pentanone is employed as a silylation agent.
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2005-272188
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2002-33314
[Patent Document 3] Japanese Laid-Open Patent Publication No. 2005-236285
[Patent Document 4] Japanese Laid-Open Patent Publication No. 2007-508691
However, the processes described in Patent Documents 1 and 2 inherently include the phenomenon, in which volatile components such as water adsorbed on pores in the microporous film vaporizes under the condition of increasing the temperature of hydrophobizing gas before the hydrophobizing gas diffuses in the microporous film, to fill the pores of the microporous film with the vaporized components, and then vaporized components, in turn, are released from the microporous film. Therefore, such phenomenon causes problems, in which a diffusion of the hydrophobizing gas within the microporous film is obstructed, so that the time required for the hydrophobizing treatment is increased.
On the other hand, when the concentration of the hydrophobizing gas is increased under the condition of elevating temperature in order to reduce the hydrophobizing processing time, the hydrophobizing gas are easily precipitated into the fine particles on the microporous film. One of the reasons for precipitating the hydrophobizing gas into the fine particles is that molecules of hydrophobizing gas mutually react under the condition of elevating temperature before the hydrophobizing gas is reached in the interior of the microporous film to extensively grow, creating fine particles, which, in turn adhere the surface of the microporous film. Another reason may be that an excessive hydrophobizing gas aggregates on the surface of the microporous film, and the hydrophobizing gas precipitates into fine particles by heating via elevating temperature. Such precipitates created from the fine particles of the hydrophobizing gas provide an inhibition to the diffusion of the hydrophobizing gas into the interior of the microporous film, failing to provide sufficient hydrophobizing effect of that microporous film. Therefore, an adsorption of water is occurred on the microporous film, causing a problem of increased specific dielectric constant.
Since the process described in Patent Document 3 involves cooling the substrate at a temperature ranging from about 100 Kelvin to about 300 Kelvin, the hydrophobizing agent is condensed on the surface of the microporous film and then the condensed liquid is dried by the heat to create the particles on the surface of the microporous film, causing a problem of failing hydrophobization in the inside of the pores of the microporous film. In addition, it is considered that, since it is heated under the presence of surplus hydrophobizing agent, surplus hydrophobizing gas agglomerates on the surface of the microporous film, so that the hydrophobizing gas precipitate into fine particles by heating via elevating temperature.
Such precipitates generated on the surface of the microporous film may cause a shape defect in the process for patterning the microporous film of the semiconductor device.
The process described in Patent Document 4 may achieve insufficient hydrophobizing treatment over the surface of the microporous film and the interior of the pore. In particular, the use of a mixture of a solvent and a silylation agent may cause a condensation of the solvent on the surface of the microporous film and in the interior of the pore in the low temperature treatment, and such condensed liquid causes a problem of generating particles on the surface of the microporous film or stuffing the inside of the pore. On the other hand, the high temperature treatment may also cause a problem of vaporizing the solvent, which is then changed to a reactive gas.
Results of the investigations of the present inventors for solving such problem show that it was found that the hydrophobization can be achieved in the inside of the pores of the microporous film, when a gaseous mixture of a silylation gas and an inert gas is employed and a temperature being equal to or higher than a dew point temperature of the silylation gas and equal to or lower than a vaporizing temperature of the silylation gas is employed for the temperature of the substrate.
According to one aspect of the present invention, there is provided a process for manufacturing a hydrophobized microporous film, including: forming a microporous film on a substrate; supplying a gaseous mixture composed of a silylation gas and an inert gas in an apparatus having the substrate disposed therein at a temperature of the substrate, the substrate having the microporous film formed thereon, and the temperature being equal to or higher than a dew point temperature of the silylation gas and equal to or lower than a vaporizing temperature of the silylation gas; stopping the supply of the gaseous mixture into the apparatus; and heating the substrate having the microporous film formed thereon.
In the process for manufacturing the hydrophobized microporous film, the gaseous mixture composed of the silylation gas and the inert gas is supplied under the condition that the temperature of the substrate in the apparatus is equal to or higher than a dew point temperature of the silylation gas and equal to or lower than a vaporizing temperature of the silylation gas. More specifically, the substrate temperature is specified as being equal to or higher than a dew point temperature of the silylation gas and equal to or lower than a vaporizing temperature of the silylation gas, on the premise that the gaseous mixture composed of the silylation gas and the inert gas is supplied. This allows penetrating the silylation gas over the surface of the microporous film and in the inside of the pores. Further, the substrate is heated once the supply of the gaseous mixture is stopped, so that the surface of the microporous film and the interior of the pores are hydrophobized with the entered silylation gas. According to the process for manufacturing the hydrophobized microporous film as described above, the process for manufacturing the hydrophobized microporous film with reduced time required for the hydrophobizing processing and reduced increase in the specific dielectric constant can be obtained.
According to the present invention, the process for manufacturing the hydrophobized microporous film with reduced time required for the hydrophobizing processing and reduced increase in the specific dielectric constant can be obtained.